The contact slips in from the back of the connector and there is spring tab that pops up into a recess to keep it from coming out. The tab can be released and the contact removed. Crimp a new contact on the wire and push the contact into the XH connector.
I haven't seen the new JK Smart BMS up close but from pics it looks like they changed the connector for the cell voltage/balance wires so the above probably does not apply.
